Generally, for a material to be suitable for use as an electrical contact, it should be non-fusing with a mating contact material and have a low, ohmic, contact resistance with a relatively small contact pressure. In addition, the material must be capable of maintaining a low resistance after a large number of operations over an extended life period and be corrosion resistant.
Among the contact materials employed in the past are the precious metals such as gold, palladium and platinum and alloys of such metals with each other as well as with metals such as silver and nickel. Due to the high cost of precious metals, a large effort has been employed to find contact materials which are substantially cheaper than the precious metals but which also possess all or many of the properties of the precious metals as mentioned above and for certain applications, are also solderable. In a recently filed copending application, Ser. No. 646,665, now U.S. Pat. No. 4,518,469 there is described nickel-antimony alloys which are suitable for use as a contact material. That patent application also describes a process for electroplating films of such contact materials employing dc plating techniques. While such dc plated films are adequate for many uses, especially where high ductility is not required, in certain other applications such as a coating over a copper wire where the wire may undergo considerable bending, high ductility is required. For such applications the dc electroplating method has been found to be inadequate due to insufficient ductility of the electroplated film.
The present invention describes a pulse plating technique for electroplating nickel-antimony films having high ductility sufficient for use for the plating of wire.